How to populate Android Room database table on first run?

Question

In SQLiteOpenHelper there is a onCreate(SQLiteDatabase ...) method which i used to populate database tables with some initial data.

Answer 1

You can populate tables after creating the database, make sure the operation is running on a separate thread. You can follow the classes bellow to pre-populate tables on the first time.

AppDatabase.kt

@Database(entities = [User::class], version = 1, exportSchema = false)
abstract class AppDatabase : RoomDatabase() {

    abstract fun userDao(): UserDao

    companion object {

        // For Singleton instantiation
        @Volatile private var instance: AppDatabase? = null

        fun getInstance(context: Context): AppDatabase {
            return instance ?: synchronized(this) {
                instance ?: buildDatabase(context).also { instance = it }
            }
        }

        private fun buildDatabase(context: Context): AppDatabase {
            return Room.databaseBuilder(context, AppDatabase::class.java, DATABASE_NAME)
                    .addCallback(object : RoomDatabase.Callback() {
                        override fun onCreate(db: SupportSQLiteDatabase) {
                            super.onCreate(db)
                            //pre-populate data
                            Executors.newSingleThreadExecutor().execute {
                                instance?.let {
                                    it.userDao().insertUsers(DataGenerator.getUsers())
                                }
                            }
                        }
                    })
                    .build()
        }
    }
}

DataGenerator.kt

class DataGenerator {

    companion object {
        fun getUsers(): List{
            return listOf(
                User(1, "Noman"),
                User(2, "Aayan"),
                User(3, "Tariqul")
            )
        }
    }

}